1. Field of the Invention
The present invention relates to a tool controlling apparatus and, more particularly, a tool controlling apparatus for executing appropriately position control and torque control of a tool acting on a work. Further, more particularly, the present invention relates to a tool controlling apparatus which can provide a high precision work with high circularity not to disturb the diameter expansion of the work during rolling process as forming process of the work.
2. Description of the Related Art
The annular body forming apparatus which is one of tool controlling apparatuses in the related art has been disclosed in Japanese Patent Examined Publication (KOKOKU) Hei 3-31534. In this apparatus, the work is sandwiched between a forming roller and a mandrel, the forming roller is rotated upon an axis which is parallel with the mandrel, and a diameter of the work is expanded by pushing the forming roller relatively against the work to roll the work while rotating the work. At this time, guide rails, etc. support the work as the annular body during the rolling process to keep circularity of the work. An outer diameter detecting lever which contacts an outer peripheral surface of the work and a sensor for detecting a displacement amount of the outer:diameter detecting lever are provided. The outer diameter of the work can be detected by the outer diameter detecting lever and the sensor during the process.
FIG. 19 is a sectional view showing the rolling situation of the annular body forming apparatus in the related art. In the rolling process by the annular body forming method in the related art, contact between a work 305 and a forming roller 315 is changed from point contact to surface contact by bringing the forming roller 315 close to the work 305 relatively in the initial feed. After the forming roller 315 has come into surface contact with the work 305, the forming roller 315 and a mandrel 304 are then brought close to each other at a predetermined quick feeding the rough feed. Thus, the work 305 is rolled by a large torque, a diameter expanding speed of the work 305 is accelerated, and the torque in the rough feed has a maximum value during the rolling process.
At this time, a pair of guide rollers 306 are employed to support an outer surface of the work 305 while fixing position of the work 305. If a work holding force by the guide rollers 306 is insufficient at this point of time, abnormal vibration is easily generated in a work rolling portion. In addition, because polygonal components are generated once the vibration is generated, it is impossible to form the round work, so that the outer diameter of the work 305 becomes uneven.
Then, when the outer diameter of the work 305 reaches a diameter to be switched to the finishing feed, a relative moving speed between the mandrel 304 and the forming roller 315 is reduced to improve the circularity of the work 305 by reducing a cutting push-down amount mm/rev (one revolution) (referred to as a xe2x80x9cdraft amountxe2x80x9d hereinafter), and then the process is shifted to the finishing feed. When it is detected that a torque in the finishing feed become a steady state and then the outer diameter of the work 305 comes up to a predetermined dimension, the rolling process is terminated.
Normally, if the torque of the guide rollers 306 is set small in the finishing feed rather than the rough feed, the diameter expansion of the work is not disturbed and thus the good working can be attained. In this manner, such a problem has existed that the stable working conditions cannot be achieved since the torque is changed largely during the rolling process. In particular, as for the hydraulic guide rollers in the related art, it has not been apparent how the pushing force against the work should be changed in respective steps of the rolling process. Therefore, it is continued to apply a constant pushing force to the work from a run-in period of the initial rolling (initial feed) to the end of the finishing feed. Particularly, if the work is guided in the finishing feed stage by the same pushing force against the work as in the rough feed stage, it is possible to spoil the circularity of the work 305. Especially, if the thin work is to be rolled, the above event which is the influence of the pushing force of the guide rollers 306 applied to the work 305 becomes prominent. In addition, because of cycle shortening, it is desired that, in respective stages from the end of the finishing feed to the release of the guide rollers 306, the guide rollers 306 must return quickly to the home position to start the next working. In this manner, according to the annular body forming apparatus in the related art, it has been difficult to attain both the improvement in working efficiency and the improvement in working precision simultaneously.
A mechanism of the guide rollers 306 is constructed such that the guide rollers 306 are fitted on both upstream and downstream sides of the position, at which the work 305 is put between the mandrel 304 and the forming roller 315 to accept the plastic working, so as to sandwich the work 305, then apply the constant force to the work 305, and then are moved back by a force generated when the diameter of the work 305 is expanded by the rolling process. In this case, the work 305 is swung to one side when one of a pair of guide rollers 306 pushes the work 305, and the other of a pair of guide rollers 306 receives such swing force at that time to absorb the swing of the work 305. This phenomenon is repeated like a so-called resonance phenomenon, so that it is difficult to stabilize the position of the work 305. Therefore, respective guide rollers must be synchronized forcibly to be opened/closed simultaneously, otherwise a one-way clutch which is set free in the direction along which the work is excessively pushed to prevent the excessive pushing of the work 305, etc. must be incorporated. In particular, if such resonance phenomenon cannot be prevented in the finishing stage, the circularity of the work 305 is degraded extremely.
In order to improve a precision of the circularity of the work, the draft amount must be reduced by setting the finishing feed employed to roll the work 305 at a low speed. At this time, unless reduction of the draft amount is carried out so as to avoid the above resonance phenomenon, the work with good thickness deviation and circularity cannot be obtained. As the result of many experiments of the rolling process, it has been found that a relationship between pushing forces of the upstream and downstream guide rollers 306 in the finishing feed has an effect on the precision of the circularity. In other words, it has been found that it is preferable that the pushing force of the guide roller applied to the work should be made small in the finishing feed rather than the rough feed, or it is important that the pushing force of the downstream guide roller is set stronger to support the work 305 than the upstream guide roller. In addition, if the small pushing forces rather than those in the rough feed are applied from both upstream and downstream guide rollers in the finishing feed, or if the strong pushing force is applied to the work by the upstream guide roller 306 when the plastic working of the work 305 is executed in the finishing feed, the circularity is deteriorated. Therefore, the upstream guide roller must be positioned away from the work 305.
When the work is rolled by increasing the draft amount since at first the work has wrong profiles of work material such as the thickness deviation, the circularity, etc., the resonance phenomenon appears apparently. Therefore, in order to prevent the resonance phenomenon, a function of strongly pushing the work by the guide rollers 306 from both the upstream and downstream sides (up to the rough feed) must be applied.
However, when the process is shifted to the finishing feed, the thickness deviation and the circularity are gradually corrected and thus the resonance phenomenon caused between the work and the guide rollers is reduced rather than the rough feed, so that the position of the work can be stabilized. FIG. 18 is a side view showing the situation of the work which is subjected to the rolling working between a forming roller and a mandrel. As shown in FIG. 18, a thickness t0 of the work prior to the rolling process is larger than a thickness ta of the work after the rolling process and an inlet velocity v1 of the work prior to the rolling process is smaller than an outlet velocity v0 of the work after the rolling process, and also the direction of the velocity is abruptly changed. Furthermore, since the work has the thickness deviation in the rough feed of the mandrel, or since the draft amount per revolution of the mandrel against the work is selected largely, the downstream rolling portion is pushed out strongly unless the guide rollers are provided, so that the position of the work becomes unstable to thus cause the vibration. If the pushing forces of the upstream and downstream guide rollers become uneven or are reduced small at the time of such unstable state, the resonance of the work is caused up and down vertically on the basis of a shaft center Xxe2x80x94X connecting a center of the mandrel and a center of the forming roller. Unless such vibration is stopped, not only the rolling process of the work becomes difficult due to the vibration but also the thickness deviation and the circularity of the work are not corrected or sometimes they become worse, and further the damage of the die is caused.
Therefore, the invention has an object to form a work with excellent circularity by applying particularly position control and torque control of guide rollers as one of tools so as to execute them selectively in respective rolling steps, more particularly, by switching the control of the work between the position control, which is executed before starting the rolling process between a mandrel and a forming roller (after the home position before the start of the initial feed) and at the time of returning the guide rollers to the home position after a finishing feed has been completed, and the torque control, which is executed to provide desired pushing forces (torques) in remaining intermediate rolling steps.
In order to achieve the above object, the present invention is characterized by providing both a position controlling unit and a pushing controlling unit of guide rollers as one of tools. Therefore, the present invention employs a servo motor (or hydraulic pushing mechanism) as one example, and controls an operation of the guide rollers for supporting the work in a mechanism which rolls the work between a mandrel as a tool for processing the work and a forming roller. In particular, a feature of the present invention resides in that the present invention is applied to control of the operation of the guide rollers among the tools. Thus, according to the present invention, there is provided a tool controlling apparatus which can work or push a work by moving the work and a tool relatively during processing of the work, and including a position controlling unit for controlling position of the tool from start of working or pushing of the work to end thereof, and a pushing controlling unit for controlling a working or pushing force of the tool, which is applied to guide the work. Where the position controlling unit denotes all the portions for controlling both contact and non-contact between the guide rollers serving as the tool and the work at high speed based on values of the current position counter and the deviation counter. The pushing controlling unit denotes all the units for controlling the pushing force (torque value of the servo motor herein) of the tool against the work in response to requests in respective rolling steps. The forming process in the present invention includes all the working steps for applying the pushing force to the work, and then an example in which the present invention is applied to the rolling process will be explained as a representative example.
More particularly, the invention applies to an annular body forming apparatus, in which the work is rolled into desired dimensional profiles by the rolling process of the work as the annular body, and including the guide rollers, which support the work so as to sandwich the shaft center (referred to as a xe2x80x9cshaft center Xxe2x80x94X linexe2x80x9d hereinafter) connecting a center of the mandrel and a center of the forming roller. Then, the annular body forming apparatus includes the position controlling unit which is utilized to control the back-and-forth position of the guide rollers, against the work in the quick feed during when the guide rollers are moved quickly close to the work and the unloading step during when the guide rollers are returned to the original position (home position) after the rolling process has been completed, and the pushing controlling unit which is utilized to control the pushing force of the guide rollers against the work in respective rolling steps which the work is rolled by the mandrel and the forming roller between the initial feed, the rough feed, and the finishing feed.
As an example of the present invention in which the servo motor is applied to the guide rollers for supporting the work, in operation, the guide rollers are moved quickly close to the work according to the position control, then the quick feed is continued before a rolling starting point of the work, then the work is held by the guide rollers at a precise position. Then the position control is switched to the torque control by the electric signal to mate with the start of the initial feed of the rolling process of the work, then this is switched to desired values in respective steps of the initial feed, the rough feed, and the finishing feed of the rolling process of the work. Further, the torque control is switched to the position control by the electric signal at the time of the rolling process termination of the work to release the holding of the work quickly and to return the guide rollers to the home position, whereby the position control and the torque control are switched by an electric signal to mate with the progress of the rolling process of the work. As a result, high precision rolling process of the work can be achieved and also the rolling process cycle of the work can be shortened.
The annular body forming apparatus includes a moving unit for moving relatively the forming roller, which is rotated with contacting the outer peripheral surface of the work serving as the annular body, and the mandrel, which can be moved relatively to contact the inner peripheral surface of the work, a pair of guide rollers for holding the rolled position of the work by rolling on the outer peripheral surface of the work, a servo motor for driving the guide rollers, and a controller for controlling the position control and the torque control, and a dimension fixing lever as an outer diameter detecting unit for detecting the outer diameter of the rolled work, whereby the work is put between the forming roller and the mandrel by approaching the forming roller and the mandrel relatively to execute the initial feed, the rough feed, and the finishing feed. According to this configuration, the control scheme of the guide rollers can be varied between the position control and the torque control and also displacement can be controlled timely in torque control.
Furthermore, as another tool control unit included in the invention, a circularity assuring unit for manufacturing stably the work with high circularity precision may be attached. According to the circularity assuring unit, both guide rollers are brought into contact with the work during the rolling process from the initial feed to the rough feed of the work, then the guide rollers are moved back with the diameter expansion due to the rolling process while applying the desired pushing force to the work to hold the work. Then the upstream guide roller is opened by the same opening angle as the downstream guide roller from the existing contact state position of the work and the guide rollers (the opening angle relative to the turning center is kept as it is) from the end point of the rough feed (entrance of the finishing feed step). That is, the upstream guide roller is opened simultaneously in linking with the opening angle of the downstream guide roller, and then the upstream guide roller is separated from the work while controlling the downstream guide roller to retreat (with the diameter expansion of the work) by the predetermined torque in the finishing feed and thus the downstream side of the work is supported and held by the downstream guide roller solely.
More particularly, the length of the downstream arm is set longer than that of the upstream arm. Here, the length of the arm denotes a length of the arm of each guide roller. The guide rollers are made to follow the outer peripheral surface of work by the angles corresponding to the lengths of respective arms in the initial feed and the rough feed, whereas the guide roller attached onto the downstream arm is made to follow the outer peripheral surface of the work while receiving the torque control, and the linking guide roll attached onto the upstream arm is away from the work in the finishing feed. In this manner, the position of the work can be stabilized merely by pushing the downstream arm (by the guide roller) with the proper torque, without pushing by the upstream arm. In other words, in order to correct the position of the work, it is desired for improvement in the circularity to reduce the upstream pushing force to xe2x80x9c0xe2x80x9d in the finishing feed step by separating the upstream guide roller from the work, while applying the torque of the downstream guide roller (not only the torque of the servo motor but also the hydraulic force may be employed), i.e., the pushing and supporting force for the work.
FIG. 6 is a diagram showing conditions for pushing the work by a downstream guide roller after releasing an upstream guide roller from the work in finishing feed step. As for the torque for driving the guide rollers, both the upstream and downstream guide rollers are retreated with the diameter expansion by the rolling of the work while contacting the outer peripheral surface of the work to apply the equal pushing force to the work in the initial feed and the rough feed, nevertheless the pushing force is applied to the work from the downstream guide roller but the upstream guide roller is released from the work not to apply the pushing force thereto in the finishing feed since the upstream and downstream guide rollers are opened (by the equal angle) simultaneously. If a reaction force which exceeds a torque set value is applied from the work 5 to the guide rollers 6 in the torque control in respective feed steps (respective rolling steps), the guide rollers 6 are pushed back until the torque is balanced with the set torque. In addition, when the rolling process by the mandrel 4, which is inserted into the work 5, and the forming roller 3 proceeds, the outer diameter of the work 5 is enlarged, as shown in FIG. 6. That is, the radius is changed from a radius Ro to a radius Rw.
The guide rollers are opened by an angle xcex802 on the upstream side and an angle xcex801 on the downstream side with respect to a turning center of the guide rollers to follow the diameter expansion of the work immediately before the finishing feed, and the guide rollers contact the outer periphery of the work. At this time, assume that an arm length of the upstream guide roller is A2, and an arm length of the downstream guide roller is A1, and A1 greater than A2. Immediately before entering the finishing feed, a distance between a work center and a turning center of the guide rollers is changed from Ro+L prior to start of the diameter expansion of the (initial) work to Rw+L in the final finishing feed step (where an expanded radius of any work is Rw). Since the arms of the upstream and downstream guide rollers are moved simultaneously (as back-and-forth movement against the work) from the state where the guide rollers come into contact with the work 5 by the angles xcex801, xcex802 at the time of starting the finishing feed, the angles xcex801, xcex802 do not become equal because of A1 greater than A2. The angles xcex801, xcex802 can be given as xcex801 greater than xcex802 by a following equation.
[Expression 1]
(Ro+rg)2=A12+(Ro+L)2xe2x88x922A1xc2x7(Ro+L)cos xcex801=A22+(Ro+L)2xe2x88x922A2xc2x7(Ro+L)cos xcex802 (1)
According to this equation, A1/A2 greater than cos xcex801 /cos xcex802 greater than 1 can be given.
∴xcex801 greater than xcex802
Therefore, in view of the situation (shown in FIG. 6) that the opening angles of the upstream and downstream guide rollers being operated simultaneously are increased by the angle xcex94xcex8 with the diameter expansion of the work, the opening angle of the downstream guide roller is increased by the angle xcex94xcex8 when it is pushed back against the torque from the downstream guide roller to the opposite side to the work, and the upstream guide roller is also opened by the angle xcex94xcex8 by the servo motor because it is opened together with the downstream guide roller. However, as a conclusion, distances between a center of the work whose diameter is expanded and centers of the guide rollers are set as S on the upstream side and K on the down stream side, S greater than K can be derived, as indicated by following equations.
[Expression 2]
Assume following equations
xcex8U=xcex802+xcex94xcex8xe2x80x83xe2x80x83(a)
xcex8L=xcex801+xcex94xcex8xe2x80x83xe2x80x83(b)
K=Rw+rGxe2x80x83xe2x80x83(c)
X=L+Rwxe2x80x83xe2x80x83(d)
as premises,
S2=X2+A22xe2x88x922A2X cos xcex8Uxe2x80x83xe2x80x83(1)
K2=X2+A12xe2x88x922A1X cos xcex8Lxe2x80x83xe2x80x83(2)
S2xe2x88x92k2=A22xe2x88x92A12+2X[A1 cos xcex8Lxe2x88x92A2 cos xcex8U]xe2x80x83xe2x80x83(3)
can be given. In Eq. (3), since A22xe2x88x92A12 less than 0,
A2X cos xcex8U less than A1X cos xcex8Lxe2x80x83xe2x80x83(4)
must be satisfied in order to provide S greater than K. Based on Eq. (4),
A1/A2 greater than cos xcex8U/cos xcex8L greater than 1xe2x80x83xe2x80x83(5)
From Eq. (1),
A12xe2x88x92A22=2(Ro+L)[A1 cos xcex801xe2x88x92A2 cos xcex802] greater than 0
can be obtained, and thus
A1/A2 greater than cos(xcex802+xcex94xcex8)/cos(xcex801+xcex94xcex8)=cos xcex8U/cos xcex8L greater than 1
can always be satisfied since the relationship of A1/A2 greater than cos xcex802/cos xcex801 can always be satisfied (since xcex801 greater than xcex802). In other words, S greater than K is needed in order to separate the upstream guide roller from the work even if the downstream guide roller comes into contact with the work when the diameter of the work is expanded, but such relationship can be satisfied by setting A1 greater than A2. (Where 0xe2x89xa7xcex801, xcex802, xcex8U, xcex8Lxe2x89xa7xcfx80/2)
More particularly, since the distance K (downstream side) is small according to the relationship of the arm length of the guide rollers A1 greater than A2, the torque control is applied at the distance K side by which the downstream guide roller contacts the work. However, the upstream guide roller does not contact the work since the distance S which is longer than K is given to the upstream guide roller. That is, the upstream guide roller is opened by the larger angle than the downstream guide roller. This corresponds to the situation that, even though the opening angle (xcex94xcex8) of the upstream guide roller is controlled by the same servo motor control as the downstream guide roller, the relationship xcex8L greater than xcex8U can be achieved because of A1 greater than A2 and thus the upstream guide roller never contacts the work. Hence, the constraint torque of the upstream guide roller for the work becomes xe2x80x9c0xe2x80x9d. Therefore, the torque control can be effected only by the downstream guide roller by creating the relationships A1 greater than A2 and xcex8L greater than xcex8U (angles to start the pushing of the guide rollers). As a result, the arm of the downstream guide roller must be set longer than that of the upstream guide roller.
More particularly, a pair of guide rollers are brought into contact with the work to oppose to each other with respect to the shaft center Xxe2x80x94X line and to push the work until the rough feed in which the draft amount by the mandrel is large, whereby the position of the work is controlled. But, the draft amount is reduced in the finishing feed, and thus difference between an inlet velocity v1 and an outlet velocity vo becomes small not to generate the vibration. That is, the position of the work can be stabilized against the shaft center Xxe2x80x94X line. Under such situation, the upstream guide roller is brought into the non-contact state to be separated from the work, whereas the downstream guide roller is brought into the contact state to apply a desired pushing force to the work. In this manner, one type of self-aligning effects to prevent the deviation is ready to stabilize the rolling process, the circularity of the work can be improved rather than the case where the pushing force is applied to both guide rollers so as to contact the work. As described above, the present invention can vary the supporting and pushing force (torque) of the guide rollers to a desired value from the initial feed to the finishing feed, and the further invention can control the torque of the downstream guide roller merely in the finishing feed after the upstream guide roller has been released, so that they can be used properly based on initial thickness deviation and the circularity of the work or the thickness of the work.